These types of electrodes are used for various clinical applications, for example electro cardiograms, electro encephalograms or electromyograms, but also for more long-term processes. These types of electrodes are thus used particularly for muscle stimulation, for example building up muscle by means of functional electrical stimulation (FES) or transcutaneous electrical nerve stimulation (TENS).
In this process, electrical signals are transmitted via the electrodes to the body of the person wearing the electrodes, such that the muscles are stimulated into movement. Alternatively, it is also possible for these types of electrodes to receive electrical signals from a muscle or the skin of the wearer and supply them for further processing.
In order to enable the transmission of electrical signals from the electrode to the body of the patient, it is necessary that the actual contact between the electrode and the patient's skin occurs via an ionically conductive medium. Only the conduction of electrical signals from the patient's skin is also possible via metallic electrodes, for example. To this effect, it is known from DE 10 2009 013 470 A1 to arrange a gel cushion with an ionically conductive liquid gel on the side of the skin facing the electrode. On the other side of the gel cushion is a liquid-tight support material for preventing the liquid gel from escaping on this side of the electrode. In order to guarantee as good an electrical contact as possible between the electrode, in particular the liquid gel in the gel cushion, and the wearer's skin, a film of gel or moisture must be formed on the patient's skin. The electrodes equipped with this hydro or liquid gel are very sticky, thereby providing a good grip on the wearer's skin, at least for a short time. In contrast, sponge electrodes become damp and greasy due to the liquid that is easily squeezed out of them.
The contacting of the ionically conductive gel cushion occurs via a metal plate or a rubber electrode. This comprises a metal snap fastener on the side facing the gel cushion with which contact can be made with an ECG device, for example, by means of its cable.
In this process, the metal plate must be in constant contact with the gel cushion in order to guarantee an electrical contacting.
A similar electrode construction is known from EP 1 021 986 A2, for example. This also contains a gel body on one of the sides of a support material facing the skin, which is filled with a conductive gel. A metallic sensor with a snap fastener connecting element is arranged on the gel cushion by means of which contact can be made with the sensor, and thereby the gel cushion. In this case the metallic sensor must also be in constant contact with the gel cushion in order to guarantee an electrical contacting.
EP 0 467 966 B1 describes an electrical stimulus electrode: in this case, the electrical signals are sent directly to the patient's skin by means of a conductive cloth. This conductive cloth comprises an arrangement of conductive fibers and is soaked with a conductive adhesive that, in this case, provides the actual contact between the electrode and the skin.
All electrodes mentioned until now are unsuitable for longer use, for example with longer treatments in the form of muscle stimulations, which often last for several days. Over the course of this period an intense movement of the skin occurs at the point of the electrodes, due to muscle contraction for example, caused by the electrical signals that are introduced into the human body by the electrodes. In addition to this, the patients move a lot over the course of several days, such that high demands are put on the electrodes in terms of mechanical resistance.
Firstly, it is a disadvantage that the gel cushions described until now are very sticky, due to the liquid gel contained within them. Should a relative movement between the skin and the electrode stuck to it now occur, as a result of movements made by the patient, the adhesive point may become detached and stick to a new point the next time the patient moves. This leads to skin irritations and is generally uncomfortable for the wearer. In addition, this type of detachment and reattachment of the electrode has the disadvantage that the electrical contact between the electrode and the patient's body is broken for at least a short period, or it is at least effected. Secondly, the relative movement between the patient's skin and the electrode may cause the electrode to move, such that its optimal position relative to the muscle that it stimulates can no longer be guaranteed or a deformation of the electrode may occur.
Alongside the self-adhesive gel cushion, contacting via a metallic sensor also has disadvantages. As a result of the intense movement that one electrode on the human body is subjected to over a period of time, the contacting may be broken, such that in the worst case, the electrical contact is interrupted and thus no more current signals can be introduced into the patient's body. This would result in the failure of the therapy.
An item of clothing is described in WO 01/02052 A2 that comprises at least two different zones, one of which is designed to be electrically conductive. Both types of fabric are sewn or knitted together. The electrically conductive zones can then be used as an electrode for medical applications.
U.S. Pat. No. 5,123,423 describes a pad for defibrillators that is attached between the defibrillator electrode and the patient's skin. Due to the emergency situation in which they are used, these pads do not have an enhanced level of wearer comfort. The pads comprise a lower layer that is made from a conductive polymer. A fibrous layer, for example made from carbon fibers, is arranged in and above this, which prevents the polymer layer from also sticking to the defibrillator electrode.
In US 2007/0049814 A1 a set of clothing items is described which has electrodes and gel reservoirs, through which electrical signals can be transmitted to stimulate the wearer's muscles that are located beneath the item of clothing.
DE 93 16 259 U1 describes an electrode which is made from a conductive polymer layer and a cover layer which covers the polymer layer. The polymer layer is poured into a recess of a foam layer in order to achieve a flush joint between the conductive and non-conductive material layers.
In DE 10 2009 017 179 A1 a device for electromyostimulation is described that is made from a suit comprising one or several parts into which integrated textile-based electrodes, moisturizers and electrical leads are incorporated.